West Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 70 to 76 near the shore to around 63 above 3000 feet. East winds up to 10 mph. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers. Highs 86 to 91 near the shore to around 78 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows 70 to 76 near the shore to around 63 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 72 to 77. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 81 to 89. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Kaua’i Mountains

Tonight: Mostly cloudy with scattered showers. Lows 66 to 71 in the valleys to around 60 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 75 to 85 in the valleys to around 67 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows around 69 in the valleys to around 60 above 4000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

North Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 67 to 75. East winds up to 15 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 77 to 87. East winds up to 15 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 67 to 75. East winds around 10 mph. Chance of rain 30 percent.

East Kaua’i

Tonight: Mostly cloudy with scattered showers. Lows 66 to 77. East winds around 10 mph. Chance of rain 50 percent.

Monday: Partly sunny with scattered showers. Highs 74 to 86. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Lows 66 to 78. East winds 10 to 15 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Weak low pressure far northwest of the islands will move further off to the west as high pressure expands over the Central Pacific. Drier air will settle in over the state over the next few days. Trade winds will generally remain moderate to locally breezy through the middle of the week, then taper off slightly. Showers will become less frequent this week and focus along windward areas.

Discussion

Along with weak upper low north northwest of the state and a lingering moist airmass provided enough instability for training heavy rain over central and northern portions of Kauai last night through this morning. A couple of stream gages along the Hanalei River reported rapid rises in water levels, resulting in downstream flooding along the stretch of Kuhio Highway in the vicinity of the Hanalei Bridge and subsequent closure of the road there. As of 2 PM HST, several sites in the higher elevations of central Kauai recorded between 1 and 5 inches of rain in the previous 12 hours and up to 5 to 7 inches in the past 24 hours. Windward slopes of the other islands, as well as leeward Big Island slopes, came in with around a quarter to one inch of rain.
A drier air mass has moved in from the east this afternoon, with the 00Z soundings from Hilo and Lihue reporting precipitable water values around a half an inch lower than 12 hours ago. This is evident in the drastic decrease in cloud and shower coverage on visible satellite over the state this afternoon. This drier and more stable pattern is expected to stick around for the coming week as ridging aloft settles in. Surface high pressure far north-northeast of the state will continue to produce a gradient tight enough to drive moderate to locally breezy trade winds over the islands for the next several days. This could result in a somewhat enhanced fire weather concerns for the already rain-starved leeward areas. The approach of a shortwave mid-level trough from the east may subtly weaken winds through the remainder of the week, but limited moisture will maintain more modest rain chances. The slightly weaker synoptic trade flow may allow local sea/land breezes to take over in some of the more sheltered leeward areas. Otherwise, expect isolated to scattered showers to move into windward areas at times through the week.

Aviation

Moderate to locally breezy trades for the next few days. Low cigs and SHRA should mainly be confined to windward and mauka locations. MVFR conds possible in SHRA otherwise VFR prevails.
AIRMET Sierra for mtn obsc remains in effect for N thru SE east sections of Kauai.

Marine

A surface high centered far to the north and a weak trough to the west will drive moderate to fresh east trade winds this week.
Small south and southwest swells will keep small surf along south facing shores through the week with a long period boost around Wednesday night. Surf along east facing shores will remain small and choppy. Surf along north facing shores will remain nearly flat through the forecast period.
Peak high tides associated with the lunar cycle could lead to minor coastal flooding along shorelines and low-lying coastal areas next week Monday through Wednesday during the daily peak tide each afternoon.

Fire weather

Due to recent rain, statewide fire weather concerns will remain low to begin the week. Drier conditions developing this week will act to increase fire weather concerns again, mainly over the leeward areas who received little rainfall from this recent event. Expect KBDI values exceeding 600 with afternoon humidities falling into the lower to middle 50s under lighter winds through much of the coming week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Kauai Now Weather is brought to you by Blue Hawaiian Helicopters.